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BF9.9 will not plane a 8 ft hard bottom inflatable

J

JanS48

New member
Greetings everyone
I've a 2018 Honda 9.9 - it came with a 4 blade prop. It is currently on an 8ft BRIG Hard bottom inflatable. When running wide open it refuses to bring the boat to a plane - the engine's cavitation plate is set even with the bottom of the boat. When WOT the stern just goes way down - no plane.
If I put an old 8 hp Nissan 2 stroke on the boat it goes to a plane nicely - but I hate the noise of the 2 stroke.
I suspect the culprit is the 4 blade prop the Honda 9.9 came with, can anyone suggest a prop that would be better suited to an 8 ft hard bottom inflatable?
Thanks in advance
Jan
 
I'm not an expert on props for these motors hence my post, however, I do know less pitch will decrease speed and increase torque - the torque is not the issue here. I suspect a 'greater' pitch 3 blade prop will fix the issue - I just don't know which one. I'll check with Sola props and see if they can make a suggestion. I was hoping someone else had a similar issue.
Thanks
Jan
 
Torque is the issue here. The engine needs to be able to reach sufficient rpm to get close to the peak of its torque curve to be able to bring the boat onto plane. Once it is on plane, the top speed will be determined by the horse power, which peaks at 5,500 rpm on that engine.

I suggest getting a cheap sparkplug wire induction tachometer like this one and measuring you rpm at WOT as you try to bring the boat on plane. If it is below 5000 rpm, decrease the pitch of the prop. If it is over 5,500 rpm, decrease it.

https://www.amazon.com/RacingPowerS...ocphy=1015057&hvtargid=pla-629833188418&psc=1
 
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